1. Field of the Invention
The present invention relates to a device for indicating that an electrode cable is correctly connected to a medical implant for emitting electrical pulses, the implant thereby being equipped with a connection part for the electrode cable's proximal end.
2. Description of the Prior Art
Various types of implantable medical devices are known in the art which include an implant and an electrode cable for delivering electrical energy to a sight within the person in whom the implant is implanted. In such devices, the electrode cable is connected mechanically and electrically to the implant by means of a connector part which contains one or more electrode connectors. In the case of a pacemaker, the connector part is usually a molded part made of transparent epoxy plastic and attached to the top of the metallic pacemaker enclosure. The electrode connectors in the molded part are electrically connected to the pacemaker circuits inside the enclosure via a number of connecting pins. The proximal end of the electrode cable is attached to the molded part with, e.g., screws. U.S. Pat. No. 5,086,773 cites such solutions in a description of the prior art. The device disclosed in U.S. Pat. No. 5,086,773 is an example of an electrode cable attachment arrangement without screws or the need for tools. This known attachment device contains at least one coil spring, arranged in a connection receptacle, for the proximal end of the electrode cable. The internal diameter of the coil spring is slightly smaller than the external diameter of the proximal end. When pressure on the connection part is relaxed, the spring resumes its normal state, thereby affixing the electrode cable and establishing electrical contact.
European Application 448 760 also provides an example of a fixation device in which a spring located in a connection receptacle is employed for attaching and seating an electrical conductor in the connection receptacle.
With electrode connection in a transparent molded part, an external visual check can be made to ensure that the connection is correct. A disadvantage with the use of a molded part of the type described above, however, is that the part takes a relatively long time to make, since the epoxy plastic needs time to cure. Another disadvantage is that cracks could develop in the molded part over time. These disadvantages can be avoided by integrating the connector into the pacemaker enclosure which would thus have a receptacle for the proximal end of the electrode cable. This type of connection is usually referred to as a "black hole" because visual inspection of its interior after the proximal end of the cable has been inserted is not possible.
U.S. Pat. No. 4,934,366 describes a pacemaker connection with a black hole-type electrode connection and shows how the proximal end of the electrode cable is attached to the pacemaker and seals the attachment area without the need for screws. Fixing is achieved using clamping rings, threaded onto the proximal end of the electrode cable when the cable is connected to the pacemaker, and springs surrounding the proximal end, the springs also serving as electrical connectors for the electrode cable.
One problem with black hole connections according of the type described in U.S. Pat. No. 4,934,366 is that no indication is provided as to whether the electrode cable has been correctly attached and seated. Physicians implanting medical implants have expressed a wish for some kind of indication showing that the connection is correct.
One device, which emits a clicking sound to confirm that the electrode cable's proximal end has been correctly connected to a device for emitting electrical pulses, is described in European Application 0 630 662. The mechanically generated clicking noise is produced by a dish-shaped disk which snaps from one position to another when the end of the electrode presses against the disk.